1 List of United States cities by population. ^ 2  Population projection is that of the entity known since 2016 as Ciudad de MÃ©xico and previously as the Distrito Federal. ^  Population estimate is that of the Toronto census division, which consists solely of the City of Toronto.
Lens (optics) For other uses, see Lens. A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.
lens. 1  a piece of glass, or other transparent substance, with two curved surfaces, or one plane and one curved, regularly bringing together or spreading rays of light passing through it: a lens or combination of lenses is used in optical instruments, eyeglasses, etc. to form an image.ens-Computer Definition. The glass or plastic elements that focus light onto analog film or a digital sensor in a still or video camera. Lens quality is just as important in digital cameras as it was in the Daguerreotype cameras in the 1800s.